1. Field of the Invention
The present invention relates to a method of forming a penetration electrode and to a substrate with an attached penetration electrode. In particular, the present invention relates to a method of forming a penetration electrode that is suitable when manufacturing a penetration electrode used in wiring in electronic devices and optical devices and the like, or in a wiring layer when a device is connected in a stack. The invention also relates to a substrate with an attached penetration electrode.
2. Description of Related Art
In order to reduce the size and raise the functionality of electronic devices and optical devices, or in order to stack these devices, a penetration electrode is sometimes used to electrically connect the front and rear surface sides of a substrate. Conventionally, this penetration electrode is manufactured, for example, by a method such as that shown in FIGS. 1A to 1C.
As is shown in FIG. 1A, wiring and a pad formed by an electroconductive thin film 2 are provided on one main surface A of a substrate 1. This wiring and pad are used for making an electrical connection with other substrates or devices.
First, as is shown in FIG. 1B, a micropore 3 is formed directly beneath the electroconductive thin film 2 extending from another main surface B of the substrate 1. Examples of the method used to form the micropore 3 include deep-reactive ion etching (DRIE) typified by inductively coupled plasma-reactive ion etching (ICP-RIE), anisotropic etching using a KOH solution or the like, and laser processing. If necessary, an insulation layer can be formed on the surfaces of the main surface B and the hole wall of the micropore 3.
Next, as is shown in FIG. 1C, an electroconductive substance 4 is inserted into the micropore 3 from the main surface B side so as to completely fill the interior of the micropore 3. The method used to insert the electroconductive substance 4 may be a molten metal insertion method or a printing method. At this time, in order to electrically connect the wiring and pad formed by the electroconductive thin film 2 with the electroconductive substance 4, a penetration electrode that penetrates between the front and rear of the substrate 1 is formed at a distal end portion of the micropore 3 (see Japanese Patent Application Laid-Open (JP-A) No. 2002-158191).
As described above, in a conventional method of forming a penetration electrode, because one end of the micropore is blocked off only by the wiring and pad formed by the electroconductive thin film, and because the electroconductive thin film is often formed having a thickness of less than several μm or less, the mechanical strength of this portion is weak and, in some cases, breakages have occurred such as the thin film breaking while being transported during the manufacturing process.
Moreover, when inserting an electroconductive paste into the micropore using a printing method, it is desirable that the printing pressure be raised a certain amount in order to achieve a highly reliable electrical connection at the distal end portion of the micropore, however, there have been cases in which, when the printing pressure is high, the inserted electroconductive paste ends up breaking through the electroconductive thin film.
The present invention was conceived in view of the above circumstances and it is an object thereof to provide a method of forming a penetration electrode in which an electroconductive substance is inserted into a micropore, one end of which is covered only by wiring and a pad formed by an electroconductive substance, without the wiring or pad being broken, and to provide a substrate with an attached penetration electrode.